Photoluminescence and radiative decay times of CsBr:In

Abstract

The photoluminescence spectra, excitation spectra and radiative decay times of CsBr:In+ have been investigated in the temperature range 4.2-300K. Excitation in the A (4.38 eV; 283 nm) absorption band at 4.2K gives rise to two partly overlapping emission bands at 2.42 and 2.75 eV. When excitation occurs in the B (4.68 eV; 265 nm) or C (5.19 eV; 239 nm) absorption bands an additional emission band at 3.25 eV is also observed. The relative intensities of these bands are strongly dependent on the wavelength of the excitation and also on the temperature. All the emission spectra were resolved into an appropriate number of skew-gaussian components. The effective frequency of the lattice vibrations coupled to the relaxed excited states was determined by moments analysis. At 4.2K the radiative decay times for the emission bands each exhibit a slow component ( approximately 10-4-10-5 s) and a fast component ( approximately 10-7-10-8). The consequences of the two phenomenological models, (i) JT>>SO and (ii) JT<<SO, where JT is the Jahn-Teller interaction and so the spin-orbit coupling, are examined. It is concluded that the latter leads to a consistent interpretation of all the experimental results.